Mars rover ordered to begin moving to planet's surface

Sojourner, a six-wheeled rover the size of a microwave oven, inched down a metal ramp and onto the frigid Martian soil Saturday night, becoming the first mobile vehicle to roll on another planet.

Then, as the rotation of Mars began to carry it out of radio contact with Earth, the pride of NASA's Pathfinder mission was to lower a sophisticated instrument to the ground and began sniffing out its new surroundings.

It was the last major planned activity on a day that began with anxiety.

The solar-powered rover had ceased communicating with the main lander Friday night, even though it was still latched to one of the main craft's three solar panels. But when the time came for the rover and Pathfinder to awaken Saturday, Sojourner was communicating just fine.

"We feel like we've been invited back to the party," rover operator Matt Wallace said.

Later, mission controllers unfurled ramps in front of and behind the rover and then decided that Sojourner would descend on the rear ramp.

The microwave oven-sized rover wasn't expected to go far.

"For the first couple of days, we'll just have a learner's permit," Wallace said.

The lander's camera team produced a complete 360-degree panorama of Pathfinder's surroundings, assembled from 120 tiny snapshots. The image looked for all the world like the U.S. Southwest, with jumbled boulders scattered about a barren, table-flat plain and hills on the distant horizon.

"It's a lot like Tucson," quipped Peter Smith, the head scientist on the camera team and a professor at the University of Arizona.

The only technical problem that remained Saturday evening concerned the lander's computer, which had spontaneously reset itself the night before. The glitch didn't cause any damage, but mission operators wanted to figure out why the computer had hiccuped before going on with the mission.

"The spacecraft is fine. The lander is fine," said mission manager Richard Cook. "But we're a little perplexed as to what happened."

Between the ramp release and the rover's departure, the lander's camera was to pop up to full height, about 51/2 feet. That would increase the height of the distant hills in the camera's panoramic photos.

"All these features that you see in the distance have the potential to double in height, because we're going to double in height," Smith said.

NASA scientists had brainstormed to fix potentially crippling problems that left the rover stuck aboard the lander with tantalizing rocks just out of reach. But in the end, it appeared that simply putting the rover to sleep during the Martian night and reawakening the following morning did the trick.

"It's just like having your screen lock up on you when you're using Microsoft Word or something. You've got to hit the reset button," Wallace said.

Rover manager Jacob Matijevic said an apparent software problem had prevented the rover's modem from sending data to the lander, Sojourner's only link to Earth. Some small packets of data got through, but larger ones were being dropped.

"We're just kind of getting one syllable across the net, but not full sentences," said deputy project manager Brian Muirhead.

By Saturday evening, mission controllers still hadn't figured out what went wrong with the rover. But they were optimistic about the vehicle's reliability.

"If it was correctable once, we feel like there's a very high probability that it could be corrected again," Wallace said.